1. Field of the Invention
The present invention relates to electric switches and, more particularly, to a press button switch having a seesaw switching mechanism for switching the circuit between on/off positions.
2. Description of the Related Art
A variety of electric switches, including seesaw switches and press button switches are known. FIG. 1 shows a press button switch 1 according to the prior art. This design uses a press button 11 to move a metal contact plate 12 between on/off positions. The metal contact plate 12 is pivoted to the end portion 15 of one terminal 14 by a hook plate 13, and moved by the push button 11 to switch on/off contacts 17 and 18 subject to the effect of a spring plate 16. This design is not suitable for high current application. For high current application, additional component parts must be added, resulting in complicated structure and high frequency of failure.
FIGS. 2A and 2B show a seesaw switch 2 according to the prior art. This design of seesaw switch 2 uses a plank 21 to move a spring 23 controlled push rod 22, causing the push rod 22 to push a metal contact plate 24 between on/off positions. This design of seesaw switch 2 is suitable for high current application.
FIG. 2C is a sectional view of a seesaw switch 20 according to Taiwan patent publication no. 320355, which was issued to the present inventor. According to this design, turning the plank 201 leftwards or rightwards switches on/off the circuit. When an overcurrent occurred, the metal contact plate 202 automatically trips off.
FIGS. 3Axcx9c3E show an overload protective press button switch according to Taiwan patent publication no. 458362. This structure of overload protective press button switch comprises a housing 31, the housing 31 having a top opening 311 and two open chambers 313 and 314 separated by a partition plate 312, a metal contact unit 33 installed in the housing 31, a switching mechanism 35, a press button assembly 32, and a linkage 34. The linkage 34 comprises a spring member 342 supported on the partition plate 312, a press member 341 mounted on the spring member 342, and a swivel holder 344 pivoted to the housing 31. The swivel holder 344 has a guide hole 343, which receives the press member 341, and a positioning portion 345 connected to the switching mechanism 35.
When pressed the press button assembly 32, the press member 341 is forced downwards to compress the spring member 342 and to bias the swivel holder 344, thereby causing the switching mechanism 35 to switch on the metal contact unit 33. When switched on, the spring member 342 pushes the press member 341 back to the initial position. The upper part I of this overload protective press button switch is similar to the design of the aforesaid prior art press button switch. The lower part II of this overload protective press button switch is similar to the design of the aforesaid prior art seesaw switch. This design is similar to Yu""s Taiwan utility model no. 83365 (equivalent to U.S. Pat. No. 5,262,748) with the exception of the additional press button assembly 32. The swivel holder 344 is equivalent to Yu""s seesaw plank. This structure of overload protective press button switch is complicated, resulting in high manufacturing cost and inconvenience of use. When the push button assembly 32 pressed to the position shown in FIG. 3C, and the swivel holder 344 is biased leftwards, the metal contact unit 33 is switched on. When the user released the hand from the push button assembly 32, the push button assembly 32 is moved to the position shown in FIG. 3D. Viewing from the outside, it shows no difference between the position of 3B and the opposition of 3D, therefore the user cannot know xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d status of the switch when viewed from the outside. For on/off indication, a complicated indicator circuit must be installed.
The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a press button switch, which enables the user to know xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d status of the switch when viewed from the outside. It is another object of the present invention to provide a press button switch, which provides the advantages of a seesaw switch. It is still another object of the present invention to provide a press button switch, which is easy and inexpensive to manufacture. It is still another object of the present invention to provide a press button switch, which has indicator means to indicate on/off status. It is still another object of the present invention to provide a press button switch, which achieves the advantages of an overload protective type seesaw switch. It is still another object of the present invention to provide a press button switch, which can easily be reset when tripped off due to an overload. To achieve these and other objects and according to one aspect of the present invention, the press button switch comprises a spring-supported press button, and a push member pivoted to the spring-supported press button and controlled by the spring-supported press button to slide along two symmetrical endless sliding tracks and to switch the seesaw switching mechanism between on/off positions. According to another aspect of the present invention, the endless sliding tracks each have a top positioning point adapted for supporting the press button in xe2x80x9conxe2x80x9d position, and a bottom positioning point adapted for supporting the press button in xe2x80x9coffxe2x80x9d position. Therefore, the user can know xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d status of the push button switch visually subject to the elevation of the push button. According to still another aspect of the present invention, the seesaw switching mechanism can be equipped with a metal contact plate that automatically trips off upon an overload.